It is known that in a silver halide photographic material, various oil soluble photographically useful compounds are introduced into a hydrophilic colloid layer to constitute a photographic material in order to exhibit various photographic functions. In this case, a hydrophobic compound is used particularly in a multilayer type photographic material in order to fix an objective photographically useful material in a specific layer. These hydrophobic compounds are oil soluble materials in many cases and are emulsified with a high boiling point organic solvent and a surface active agent in order to introduce them into the hydrophilic colloid layer. They are applied via a coating process.
However, use of the high boiling point organic solvent is disadvantageous. For example, where a dye-forming coupler is used as the hydrophobic compound, a stain results on the surface of the photographic material due to the bleeding of the high boiling point organic solvent during storage of the photographic material. Also, there is degradation of coloring performance attributable to deterioration of reactivity due to crystal deposition of the coupler. In particular, where a dye is used as the hydrophobic compound, the problems discussed below result.
In a silver halide photographic material, a photographic emulsion layer and the other hydrophilic colloid layers are often colored for the purpose of absorbing light of a specific wavelength range.
When it is necessary to control the spectral composition of light incident to a photographic emulsion layer, a coloring layer is usually provided farther from a support than the photographic emulsion layer. Such a coloring layer is called a filter layer. Where plural photographic emulsion layers are present, the filter layer is provided at the middle thereof in some cases.
For the purpose of preventing blur of an image, that is, a halation caused by a light which is scattered in or after passing through a photographic emulsion layer and is reflected on an interface between the emulsion layer and support or a surface of a support side opposite to the emulsion layer to get once again in the photographic emulsion layer, a coloring layer which is called an anti-halation layer is provided between the photographic emulsion-layer and support or on a support side opposite to the photographic emulsion layer. Where plural photographic emulsion layers are present, the anti-halation layer is provided at the middle thereof in some cases.
The photographic emulsion layer is sometimes colored in order to prevent the deterioration of the sharpness of an image (in general, this phenomenon is called an irradiation) caused by scattering of light in the photographic emulsion layer.
Dyes are usually incorporated into these hydrophilic colloid layers to be colored. These dyes are required to satisfy the following conditions:
(1) having an appropriate spectral absorption according to a particular use;
(2) photochemically inactive, that is, exerting no adverse affects in a chemical sense, for example, reduction of a sensitivity, degradation of a latent image and fogging, to the characteristics of a silver halide photographic layer;
(3) bleached at the photographic processing steps or eluted in a processing solution or rinsing water to leave no harmful color on a processed photographic material;
(4) not diffused from a colored layer to the other layers; and
(5) having an excellent aging stability in a solution or a photographic material and not discolored and faded.
In particular, where the coloring layer is a filter layer or an anti-halation layer provided on the same side of a support as a photographic emulsion layer, it is necessary in many cases that those layers are selectively colored and that the other layers are not substantially colored, because otherwise not only a harmful spectral effect is exerted to the other layers but also an effect as the filter layer or anti-halation layer is reduced. However, the layer containing a dye contacts the other hydrophilic layers in a wet condition and after permits a part of the dye to diffuse from the former to the latter. Many efforts have so far been made in order to prevent such dye diffusion.
For example, methods are disclosed in U.S. Pat. Nos. 2,548,564, 4,124,386 and 3,625,694, in which a hydrophilic polymer having a charge opposite to a dissociated anionic dye acts as a mordant in a layer to localize the dye in a specific layer by means of an interaction with a dye molecule.
However, such a fixing/decoloring method in which mordant is used requires a significant amount of the mordant for an anionic dye and therefore inevitably increases the thickness of a coloring layer. For example, when a mordant is used in a filter layer for a photographing material, the increase in the thickness of the layer causes deterioration of the sharpness of an image obtained. Further, when a mordant is used, decoloring of a sensitizing dye used for a silver halide emulsion as well as the fixing/decoloring of a coloring dye must be avoided. However, decoloring performance thereof does not always produce a high image quality of a photographic material and is not necessarily compatible with recent advances in film processing.
Further, methods in which a specific layer is colored with a water insoluble solid dye are disclosed in JP-A-56-12639 (the term "JP-A" as used herein means an unexamined published Japanese patent application), JP-A-55-155350, JP-A-55-155351, JP-A-63-27838, and JP-A-63-197943, European Patents 15,601, 274,723, 276,566 and 299,435, U.S. Pat. No. 4,803,150, and International Patent WO88/04794.
Further, methods in which a specific layer is colored with metal salt fine particles on which the dyes are adsorbed are disclosed in U.S. Pat. Nos. 2,719,088, 2,496,841 and 2,496,843, and JP-A-60-45237.
Such coloring methods have excellent fixing performances/decoloring performances but light absorption by layers manufactured by those methods are generally broad. For example, where they are used as a filter dye to the ray having some specific wavelength, problems have often been caused.
The means for dispersing an oil soluble dye together with a high boiling point organic solvent are disclosed in JP-A-61-204630, JP-A-61-205934, JP-A-62-32460, JP-A-62-56958, JP-A-62-92949, JP-A-62-222248, JP-A-63-40143, JP-A-63-184749, and JP-A-63-316852.
However, the use of such high boiling point organic solvents softens a coloring layer and deteriorates layer strength. Accordingly, more gelatin is required which results in increasing layer thickness.
Meanwhile, methods in which a solution of a hydrophobic compound, such as a dye dissolved in an organic solvent, is added and impregnated into an aqueous dispersion (a polymer latex) of a polymer and the polymer is charged therein with the hydrophobic compound, are disclosed in JP-B-51-39853 (the term "JP-B" as used herein means an unexamined Japanese patent publication), JP-A-51-59943, JP-A-53-137131, JP-A-54-32552, JP-A-54-107941, JP-A-56-126830, and JP-A-58-149038, and U.S. Pat. Nos. 4,199,363, 4,203,716, and 4,990,435. While the various problems attributable to the above high boiling point organic solvents are eliminated from these methods by the use of the polymers, the polymer latex particles lack stability during impregnating such that a flocculation is liable to take place. Moreover, a significant amount of the polymers are required for sufficiently impregnating the hydrophobic compound, and elimination of the water soluble auxiliary organic solvent used for impregnation requires a significant amount of labor and the process itself requires a long time and is complicated.
Various investigations made by the present inventors have resulted in finding that the selective coloring of a specific layer and decoloring as a processing step are possible by using a dispersion obtained by emulsifying and dispersing a mixed solution containing a water insoluble and organic solvent soluble polymer and an oil soluble dye without exerting an adverse effect on membrane strength. However, the compatibility of the organic solvent soluble polymer with the oil soluble dye is not necessarily sufficient. In particular, there have been problems with respect to the low solubility of the polymer in an organic solvent and the broadened absorption and lowered absorption strength in a maximum absorption wavelength of a dye having a high melting point.
Countermeasures against these problems are possible to some extent by increasing the proportion of the polymer used for a dispersion or using, in combination, a high boiling organic solvent in a dye dispersion. However, any of these countermeasures increases the layer thickness of a coloring layer and adversely impacts upon the requirement of making a membrane thinner for a higher image quality.